Ty800 is a live attenuated Salmonella typhi organism intended to be used as a prophylactic single dose oral vaccine for Typhoid fever. Ty800 may have advantages in several respects to current Typhoid fever vaccines, and consequently could be a significant advance when it reaches the market. Ty800 has been given to a limited number of human subjects and immunogenicity has been demonstrated. The goal of this Phase I SBIR grant is to conduct an initial series of experiments to, in part, demonstrate that Ty800 has the necessary basic elements to be a viable marketed human vaccine. Consequently, the specific aims of this proposal during the requested funding period are to 1) determine a protocol for the in vivo Ty800 General Safety Test, suitable to meet the regulations for product release, and to perform an initial GLP General Safety Test using this protocol; 2) perform preliminary evaluations of a Ty800 immunogenicity animal model, with the goal of helping define an animal model for future toxicology studies; 3) develop immunochemistry assays to evaluate the immunogenicity of Ty800 in preclinical animal models and to help define the assays to be used in future clinical trials; 4) evaluate the environmental release survivability of Ty2 and Ty800; 5) determine the antibiotic sensitivity profile of Ty800 using the Kirby-Bauer Method; 6) demonstrate the precise genetic deletion at the phoP/phoQ regulon by sequencing the Ty800 chromosomal DNA. [unreadable] [unreadable]